Wojtek,
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Is your power supply voltage dropping?? Strangely, the drain voltages drop when you key the mic.? This could suggest that T7 has an issue.? Confirm that you are seeing the drain voltage drop on the IRF510s.
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Does the bias control work?? Can you adjust the radio's current when following the set bias process?? From sbitx.net:
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How to set the bias
Siegfried Jackstien, DG9BFC (modified by me for v3 circuits)
- Set both the POTS to the minimum current
- Select Mode as USB. Reduce the MIC to zero.
- Set the Drive Level to 1
- Press the PTT.
- Without speaking into the microphone, Note the current.
- Keep the PTT on the microphone pressed, and increase the PA_BIAS POT until the current increases by another 200 mA.
- Release the PTT.
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The above is for the V3 or radios that have been upgraded, not the prior versions that have not been modified.? The Drive_Bias pot is either not there or has been disconnected in the upgrade to the V3 PA design.
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73
Evan
AC9TU
